1. Field of The Invention
The present invention relates to an optical recording/reproducing method and apparatus that records information onto or reproduces information from a storage medium, such as an optical disk, by focusing a light beam, emitted by a light source, onto a recording layer of the storage medium.
2. Description of The Related Art
Recently, there are various optical storage media that are provided for recording and reproducing of information, including CD-DA, CD-ROM, CD-R (compact disk recordable), DVD-ROM, DVD-R (digital versatile disk recordable), etc.
Japanese Laid-Open Patent Application No.11-134691 discloses an optical recording/reproducing method which determines an optimum recording power based on a relationship between the modulation parameters and the recording powers. In this method, a test writing is first performed in which writing a pattern of marks and spaces to an optical storage medium with a recording power is repeated by sequentially changing the recording power with increments. A test reading is next performed in which reading the pattern from the storage medium is repeated, so that data signals are reproduced from the respective patterns on the storage medium. A modulation parameter is then calculated for each of the reproduced data signals, each modulation parameter corresponding to one of the respective recording powers. Then, an optimum recording power is determined based on the relationship between the modulation parameters and the recording powers.
However, in the optical recording/reproducing method of the above document, the algorithm to determine the optimum recording power is inadequate for accurately checking the rising slope of the modulation parameter related to the reproduced data signal. In the optical recording/reproducing method of the above document, variations of the optimum recording power may be produced due to inaccurate checking of the rising slope of the modulation parameter.
Generally, the effective range of the write power, which is supplied to the laser diode, that the laser beam emitted by the laser diode and focused on the storage medium starts forming a mark on the storage medium is very narrow. On the other hand, the locations of the storage medium to which the test patterns are written are limited, and an increase of the amount of increments to the write power level or an increase of the number of the cycles of the test writing/reading will not be an appropriate solution to the problem of inaccurate checking of the rising slope of the modulation parameter.
For example, the recording power is sequentially changed with increments of 1.0 mW from 10.0 mW to 19.0 mW, which falls within a range of xc2x130% centered around 15.0 mW. In this case, the test writing is repeated ten times by sequentially changing the recording power with such increments.
In a case of CD-RW media, a phase-change recording material is used in the recording layer of the optical disk. The effective range of write power supplied to the laser diode that enables the emitted laser beam focused on the disk to form a mark on the storage medium is very narrow. If the write power is increased by 1 or 2 mW, the amplitude of the reproduced data signal becomes considerably large. Specifically, even if the reproduced signal amplitude is about 0.1 (noise level) at the write power p=14 mW, the reproduced signal amplitude abruptly rises to a high level of 0.5 to 1.4 at the write power p=15 mW that is incremented from 14 mW.
Accordingly, it is desirable that the algorithm to determine the optimum recording power includes a data selection procedure for accurately checking the rising slope of the modulation parameter related to the reproduced data signal. As described above, if the checking of the rising slope of the modulation parameter related to the reproduced data signal is inaccurate, variations of the optimum recording power may be produced.
An object of the present invention is to provide an optical recording/reproducing method and apparatus that minimizes variations of the optimum recording power through a recording power control algorithm that accurately checks the rising slope of the modulation parameter related to the reproduced data signal.
Another object of the present invention is to provide an optical recording/reproducing method that minimizes variations of the optimum recording power through a recording power control algorithm, so that the optimum recording power is accurately determined without being affected by noise.
Another object of the present invention is to provide an optical recording/reproducing apparatus that minimizes variations of the optimum recording power through a recording power control algorithm, so that the optimum recording power is accurately determined without being affected by noise.
The above-mentioned objects of the present invention are achieved by an optical recording/reproducing method which comprises the steps of: performing a test writing in which writing a pattern of marks and spaces to an optical storage medium with a recording power p is repeated by sequentially changing the recording power p with increments of a predetermined power; performing a test reading in which reading the pattern from the storage medium is repeated, so that data signals are reproduced from the respective patterns on the storage medium; calculating a modulation parameter m for each of the reproduced data signals, each modulation parameter corresponding to one of the respective recording powers; and determining an optimum recording power based on a relationship between the modulation parameters and the respective recording powers, wherein the determining step comprises the steps of: selecting, from all of the modulation parameters and the recording powers, a sequence of pairs of the modulation parameter m and the recording power p; calculating a gamma=(xcex94m/m)/(xcex94p/p) for each of the selected pairs of the modulation parameter m and the recording power p, the gamma defining a ratio of a change of the modulation parameter m, normalized by a modulation parameter value, to a change of the recording power p, normalized by a recording power value; and finding a target recording power corresponding to the optimum recording power based on a function derived from a relationship between the calculated gammas and the respective recording powers, the target recording power causing a value of the function to be equal to zero, wherein, in the selecting step, a pair of the modulation parameter m and the recording power p is omitted if a value of the modulation parameter of the pair is not larger than a first threshold value th1, and a pair of the modulation parameter m and the recording power p is selected if a value of the modulation parameter of a following pair first exceeds the first threshold value th1.
The above-mentioned objects of the present invention are achieved by an optical recording/reproducing method which comprises the steps of: performing a test writing in which writing a pattern of marks and spaces to an optical storage medium with a recording power p is repeated by sequentially changing the recording power p with increments of a predetermined power; performing a test reading in which reading the pattern from the storage medium is repeated, so that data signals are reproduced from the respective patterns on the storage medium; calculating a modulation parameter m for each of the reproduced data signals, each modulation parameter corresponding to one of the respective recording powers; and determining an optimum recording power based on a relationship between the modulation parameters and the respective recording powers, wherein the determining step comprises the steps of: selecting, from all of the modulation parameters and the recording powers, a sequence of pairs of the modulation parameter m and the recording power p; approximating the modulation parameter into a continuous function m(p) of the recording power p based on the selected pairs of the modulation parameter m and the recording power p; and finding a target recording power corresponding to the optimum recording power, based on a derivative function (dm/dp) of the function m(p) with respect to the recording power p, the target recording power causing a value of (dm/dp)*(p/m) to be equal to a predetermined value, wherein, in the selecting step, a pair of the modulation parameter m and the recording power p is omitted if a value of the modulation parameter of the pair is not larger than a first threshold value th1, and a pair of the modulation parameter m and the recording power p is selected if a value of the modulation parameter of a following pair first exceeds the first threshold value th1.
The above-mentioned objects of the present invention are achieved by an optical recording/reproducing method which comprises the steps of: performing an initial test writing in which writing a pattern of marks and spaces to an optical storage medium with a recording power p is repeated by sequentially changing the recording power p with first increments of a predetermined power; performing an initial test reading in which reading the pattern from the storage medium is repeated, so that data signals are reproduced from the respective patterns on the storage medium; calculating a first modulation parameter m for each of the reproduced data signals, each first modulation parameter corresponding to one of the respective recording powers; setting a first recording power pth by finding a pair of the first modulation parameter m and the recording power p, from among all pairs of the first modulation parameters and the respective recording powers, a value of the first modulation parameter of the pair first exceeding a first threshold value th; performing a secondary test writing in which writing the pattern of marks and spaces to the storage medium with the recording power p, substantially centered on the first recording power pth, is repeated by sequentially changing the recording power p with second smaller increments of a predetermined power; performing a secondary test reading in which reading the pattern from the storage medium is repeated, so that data signals are reproduced from the respective patterns on the storage medium; calculating a second modulation parameter m for each of the reproduced data signals, each second modulation parameter corresponding to one of the respective recording powers; selecting, from all of the second modulation parameters and the recording powers, a sequence of pairs of the second modulation parameter m and the recording power p; calculating a gamma=(xcex94m/m)/(xcex94p/p) for each of the selected pairs of the second modulation parameter m and the recording power p, the gamma defining a ratio of a change of the second modulation parameter m, normalized by a modulation parameter value, to a change of the recording power p, normalized by a recording power value; and finding a target recording power corresponding to an optimum recording power based on a function derived from a relationship between the calculated gammas and the respective recording powers, the target recording power causing a value of the function to be equal to zero.
The above-mentioned objects of the present invention are achieved by an optical recording/reproducing method which comprises the steps of: performing an initial test writing in which writing a pattern of marks and spaces to an optical storage medium with a recording power p is repeated by sequentially changing the recording power p with first increments of a predetermined power; performing an initial test reading in which reading the pattern from the storage medium is repeated, so that data signals are reproduced from the respective patterns on the storage medium; calculating a first modulation parameter m for each of the reproduced data signals, each first modulation parameter corresponding to one of the respective recording powers; setting a first recording power pth by finding a pair of the first modulation parameter m and the recording power p, from among all pairs of the first modulation parameters and the respective recording powers, a value of the first modulation parameter of the pair first exceeding a first threshold value th; performing a secondary test writing in which writing the pattern of marks and spaces to the storage medium with the recording power p, substantially centered on the first recording power pth, is repeated by sequentially changing the recording power p with second smaller increments of a predetermined power; performing a secondary test reading in which reading the pattern from the storage medium is repeated, so that data signals are reproduced from the respective patterns on the storage medium; calculating a second modulation parameter m for each of the reproduced data signals, each second modulation parameter corresponding to one of the respective recording powers; selecting, from all of the second modulation parameters and the recording powers, a sequence of pairs of the second modulation parameter m and the recording power p; approximating the second modulation parameter into a continuous function m(p) of the recording power p based on the selected pairs of the second modulation parameter m and the recording power p; and finding a target recording power corresponding to an optimum recording power, based on a derivative function (dm/dp) of the function m(p) with respect to the recording power p, the target recording power causing a value of (dm/dp)*(p/m) to be equal to a predetermined value,
The above-mentioned objects of the present invention are achieved by an optical recording/reproducing apparatus comprising: a test writing unit which performs a test writing in which writing a pattern of marks and spaces to an optical storage medium with a recording power p is repeated by sequentially changing the recording power p with increments of a predetermined power; a test reading unit which performs a test reading in which reading the pattern from the storage medium is repeated, so that data signals are reproduced from the respective patterns on the storage medium; a calculation unit which calculates a modulation parameter m for each of the reproduced data signals, each modulation parameter corresponding to one of the respective recording powers; and a determination unit which determines an optimum recording power based on a -relationship between the modulation parameters and the respective recording powers, wherein the determination unit comprises: a selection unit which selects, from all of the modulation parameters and the recording powers, a sequence of pairs of the modulation parameter m and the recording power p; a gamma calculation unit which calculates a gamma=(xcex94m/m)/(xcex94p/p) for each of the selected pairs of the modulation parameter m and the recording power p, the gamma defining a ratio of a change of the modulation parameter m, normalized by a modulation parameter value, to a change of the recording power p, normalized by a recording power value; and a target recording power unit which finds a target recording power corresponding to the optimum recording power based on a function derived from a relationship between the calculated gammas and the respective recording powers, the target recording power causing a value of the function to be equal to zero, wherein the selection unit omits a pair of the modulation parameter m and the recording power p if a value of the modulation parameter of the pair is not larger than a first threshold value th1, and selects a pair of the modulation parameter m and the recording power p if a value of the modulation parameter of a following pair first exceeds the first threshold value th1.
The above-mentioned objects of the present invention are achieved by an optical recording/reproducing apparatus comprising: test writing unit which performs a test writing in which writing a pattern of marks and spaces to an optical storage medium with a recording power p is repeated by sequentially changing the recording power p with increments of a predetermined power; a test reading unit which performs a test reading in which reading the pattern from the storage medium is repeated, so that data signals are reproduced from the respective patterns on the storage medium; a calculation unit which calculates a modulation parameter m for each of the reproduced data signals, each modulation parameter corresponding to one of the respective recording powers; and a determination unit which determines an optimum recording power based on a relationship between the modulation parameters and the respective recording powers, wherein the determination unit comprises: a selection unit which selects, from all of the modulation parameters and the recording powers, a sequence of pairs of the modulation parameter m and the recording power p; an approximation unit which approximates the modulation parameter into a continuous function m(p) of the recording power p based on the selected pairs of the modulation parameter m and the recording power p; and a target recording power unit which finds a target recording power corresponding to the optimum recording power, based on a derivative function (dm/dp) of the function m(p) with respect to the recording power p, the target recording power causing a value of (dm/dp)*(p/m) to be equal to a predetermined value, wherein the selection unit omits a pair of the modulation parameter m and the recording power p if a value of the modulation parameter of the pair is not larger than a first threshold value th1, and selects a pair of the modulation parameter m and the recording power p if a value of the modulation parameter of a following pair first exceeds the first threshold value th1.
The above-mentioned objects of the present invention are achieved by an optical recording/reproducing apparatus comprising: a first test writing unit which performs an initial test writing in which writing a pattern of marks and spaces to an optical storage medium with a recording power p is repeated by sequentially changing the recording power p with first increments of a predetermined power; a first test reading unit which performs an initial test reading in which reading the pattern from the storage medium is repeated, so that data signals are reproduced from the respective patterns on the storage medium; a first calculation unit which calculates a first modulation parameter m for each of the reproduced data signals, each first modulation parameter corresponding to one of the respective recording powers; a recording power unit which sets a first recording power pth by finding a pair of the first modulation parameter m and the recording power p, from among all pairs of the first modulation parameters and the respective recording powers, a value of the first modulation parameter of the pair first exceeding a first threshold value th; a second test writing unit which performs a secondary test writing in which writing the pattern of marks and spaces to the storage medium with the recording power p, substantially centered on the first recording power pth, is repeated by sequentially changing the recording power p with second smaller increments of a predetermined power; a second test reading unit which performs a secondary test reading in which reading the pattern from the storage medium is repeated, so that data signals are reproduced from the respective patterns on the storage medium; a second calculation unit which calculates a second modulation parameter m for each of the reproduced data signals, each second modulation parameter corresponding to one of the respective recording powers; a selection unit which selects, from all of the second modulation parameters and the recording powers, a sequence of pairs of the second modulation parameter m and the recording power p; a gamma calculation unit which calculates a gamma=(xcex94m/m)/(xcex94p/p) for each of the selected pairs of the second modulation parameter m and the recording power p, the gamma defining a ratio of a change of the second modulation parameter m, normalized by a modulation parameter value, to a change of the recording power p, normalized by a recording power value; and a target recording power unit which finds a target recording power corresponding to an optimum recording power based on a function derived from a relationship between the calculated gammas and the respective recording powers, the target recording power causing a value of the function to be equal to zero.
The above-mentioned objects of the present invention are achieved by an optical recording/reproducing apparatus comprising: a first test writing unit which performs an initial test writing in which writing a pattern of marks and spaces to an optical storage medium with a recording power p is repeated by sequentially changing the recording power p with first increments of a predetermined power; a first test reading unit which performs an initial test reading in which reading the pattern from the storage medium is repeated, so that data signals are reproduced from the respective patterns on the storage medium; a first calculation unit which calculates a first modulation parameter m for each of the reproduced data signals, each first modulation parameter corresponding to one of the respective recording powers; a recording power unit which sets a first recording power pth by finding a pair of the first modulation parameter m and the recording power p, from among all pairs of the first modulation parameters and the respective recording powers, a value of the first modulation parameter of the pair first exceeding a first threshold value th; a second test writing unit which performs a secondary test writing in which writing the pattern of marks and spaces to the storage medium with the recording power p, substantially centered on the first recording power pth, is repeated by sequentially changing the recording power p with second smaller increments of a predetermined power; a second test reading unit which performs a secondary test reading in which reading the pattern from the storage medium is repeated, so that data signals are reproduced from the respective patterns on the storage medium; a second calculation unit which calculates a second modulation parameter m for each of the reproduced data signals, each second modulation parameter corresponding to one of the respective recording powers; a selection unit which selects, from all of the second modulation parameters and the recording powers, a sequence of pairs of the second modulation parameter m and the recording power p; a function approximation unit which approximates the second modulation parameter into a continuous function m(p) of the recording power p based on the selected pairs of the second modulation parameter m and the recording power p; and a target recording power unit which finds a target recording power corresponding to an optimum recording power, based on a derivative function (dm/dp) of the function m(p) with respect to the recording power p, the target recording power causing a value of (dm/dp)*(p/m) to be equal to a predetermined value.
In the optical recording/reproducing method and apparatus of the present invention, when selecting a sequence of pairs of the modulation parameter and the recording power, a pair of the modulation parameter and the recording power is omitted if a value of the modulation parameter of that pair is not larger than a threshold value, and a pair of the modulation parameter m and the recording power p is selected if a value of the modulation parameter of a following pair first exceeds the threshold value.
The recording power control algorithm according to the present invention accurately checks the rising slope of the modulation parameter related to the reproduced data signal, and the optical recording/reproducing method and apparatus of the present invention are effective in minimizing variations of the optimum recording power through the recording power control algorithm and in accurately producing the optimum recording power without being affected by noise. As the selection of an improper recording power can be safely prevented, the optical recording/reproducing method and apparatus of the present invention can provide good recording characteristics and protect the light source of the optical pickup and the recording layer of the optical disk against damage.